I need to know details of how java implements the function Color.RGBtoHSB(r, g, b, hsb). Does they normalize r,g,b

Question

I do not know whether Color.RGBtoHSB(r, g, b, hsb) function normalize the r,g,b before converting it to H,S,B or where i can get the java implementation of their built in functions.

Answer 1

Here is the implementation, from Color class source code directly:

public static float[] RGBtoHSB(int r, int g, int b, float[] hsbvals) {
float hue, saturation, brightness;
if (hsbvals == null) {
    hsbvals = new float[3];
}
    int cmax = (r > g) ? r : g;
if (b > cmax) cmax = b;
int cmin = (r < g) ? r : g;
if (b < cmin) cmin = b;

brightness = ((float) cmax) / 255.0f;
if (cmax != 0)
    saturation = ((float) (cmax - cmin)) / ((float) cmax);
else
    saturation = 0;
if (saturation == 0)
    hue = 0;
else {
    float redc = ((float) (cmax - r)) / ((float) (cmax - cmin));
    float greenc = ((float) (cmax - g)) / ((float) (cmax - cmin));
    float bluec = ((float) (cmax - b)) / ((float) (cmax - cmin));
    if (r == cmax)
    hue = bluec - greenc;
    else if (g == cmax)
        hue = 2.0f + redc - bluec;
        else
    hue = 4.0f + greenc - redc;
    hue = hue / 6.0f;
    if (hue < 0)
    hue = hue + 1.0f;
}
hsbvals[0] = hue;
hsbvals[1] = saturation;
hsbvals[2] = brightness;
return hsbvals;
}

Answer 2

Just open up Eclipse - Ctrl+Shift+T (open type), type in Color, find the one in java.awt - and voila. Works for most built in types.

Answer 3

RGB isn't normalized first. It's normalized during and generally just into the correct ranges. So brightness is the largest component and brightness is normalized from 0-255 range to 0-1 range. Saturation is like this as well, it's the distance from the largest component to the smallest component and squeezed into a 0-1 range. And hue is the angle in the color wheel. But, no it's converted directly into HSV and not normalized through something like sRGB (sRGB is RGB/255 and normalized into 0-1 range).

But, you shouldn't really need to know this at all. It converts into HSB. Can you get rounding errors if you convert back and forth a bunch. Sure, you can. Other than this it doesn't matter if it scales RGB to 1 or 1,000,000, it converts to a completely different way of representing colors in ranges between 0-1.

Answer 4

Note: the hue returned from Color.RGBtoHSB is normalized between 0.0 and 1.0, not between 0 and 255: ```

public static void main(String[] args) {
        float[] hsbvals = new float[3];
        Random random = new Random();
        for(int i=0;i<20;i++) {
            Color.RGBtoHSB(random.nextInt(256),random.nextInt(256),random.nextInt(256),hsbvals);
            System.out.println(Arrays.toString(hsbvals));
        }
    }

```